Electromagnetic Wave Resonator Radial Refractive Index Gradient
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Solution Overview
Problem
Ring resonators in optical communications face challenges with small evanescent fields that hinder electromagnetic coupling to surrounding materials, leading to inefficient light confinement and coupling, particularly in high refractive index materials, and difficulties in achieving critical coupling due to fabrication variations.
Innovation Solution
The design of an electromagnetic wave resonator with a structure that exhibits a decreasing effective refractive index and density radially outward, utilizing peripheral features such as teeth or wedges, which allows for improved coupling to surrounding materials by delocalizing waves and minimizing propagation losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a high refractive index material is used for the ring to enable tight bends and dense integration, then the light confinement in the ring is improved, but the evanescent field strength decreases and coupling to surrounding material becomes insufficient
Solution Approach 1:
The patent applies local quality by creating a non-uniform refractive index distribution within the ring resonator structure. Specifically, the refractive index is engineered to decrease radially from the inner region to the outer region of the ring, forming a gradient profile. This local variation in optical properties allows the inner high-index region to provide strong light confinement while the outer lower-index region enhances evanescent field extension into the surrounding cladding, thereby resolving the contradiction between confinement and coupling strength
Solution Approach 2:
The patent implements parameter changes by systematically varying the refractive index parameter across the ring cross-section. The effective refractive index is transformed from a uniform value to a graded distribution ne(r) that decreases with radial distance from the ring center. This parameter transformation enables simultaneous optimization of both light confinement (through the high-index core) and evanescent field coupling (through the lower-index cladding region), directly addressing the technical contradiction
2Productivity
If the coupling strength is increased by reducing the distance between the ring and neighboring waveguide, then the coupling efficiency is improved, but fabrication variations cause difficulty in achieving critical coupling
Solution Approach 1:
The patent changes the refractive index parameter to create a gradient profile that extends the evanescent field into the surrounding cladding region. This parameter modification increases the coupling strength inherently through the optical field distribution rather than through geometric proximity, thereby improving coupling efficiency without relying on tight dimensional tolerances that would be sensitive to fabrication variations
3Stability of the object's composition
If the peak intensity is confined in the high index material, then the light confinement is improved, but the intensity is not available for coupling to surrounding material making optical trapping difficult
Solution Approach 1:
The patent applies local quality by creating distinct regions within the ring resonator with different refractive index characteristics. The inner region maintains high refractive index for strong intensity confinement and light guiding, while the outer region has lower refractive index that allows the evanescent field to extend into the surrounding cladding. This spatial differentiation of optical properties enables the peak intensity to remain confined in the high-index material while simultaneously providing available intensity for coupling to surrounding material through the extended evanescent field in the lower-index region
Solution Approach 2:
The patent transforms the uniform refractive index parameter into a graded distribution that varies radially across the ring structure. This parameter change creates a smooth transition from the high-index core to the lower-index cladding region, allowing the optical field to be confined where needed while extending the evanescent tail for coupling purposes, thereby resolving the contradiction between intensity confinement and coupling availability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances coupling efficiency to surrounding materials, enabling stronger light-matter interactions and overcoming fabrication challenges, achieving higher quality factors and efficient light propagation.
Implementation Method 1
an effective refractive index ne(r), as obtained from angularly averaging a refractive index of the material in the plane, decreases within said region
Data Source
AI summary
An electromagnetic wave resonator comprising a body, wherein the body: has a structure extending essentially in a plane (r, θ), comprises a material in a region between limit radii ri and ro, where 0≦ri<ro and ro corresponds to a radius of a convex hull () of the structure; and allows for electromagnetic wave propagation, and wherein an effective refractive index ne(r), as obtained from angularly averaging a refractive index of the material in the plane (r, θ), decreases within said region.